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Publications in Scientific Journals:

K. Pernstich, S. Haas, D. Oberhoff, C. Goldmann, D. Gundlach, B. Batlogg, A. Rashid, G. Schitter:
"Threshold voltage shift in organic FETs by dipole-monolayers on the gate insulator";
Journal of Applied Physics, 96 (2004), 11; 6431 - 6438.



English abstract:
We demonstrate controllable shift of the threshold voltage and the turn-on voltage in pentacene thin
film transistors and rubrene single crystal field effect transistors (FET) by the use of nine
organosilanes with different functional groups. Prior to depositing the organic semiconductors, the
organosilanes were applied to the SiO2 gate insulator from solution and form a self-assembled
monolayer (SAM). The observed shifts of the transfer characteristics range from −2 to 50 V and
can be related to the surface potential of the layer next to the transistor channel. Concomitantly the
mobile charge carrier concentration at zero gate bias reaches up to 4x10^12/cm2. In the single
crystal FETs the measured transfer characteristics are also shifted, while essentially maintaining the
high quality of the subthreshold swing. The shift of the transfer characteristics is governed by the
built-in electric field of the SAM and can be explained using a simple energy level diagram. In the
thin film devices, the subthreshold region is broadened, indicating that the SAM creates additional
trap states, whose density is estimated to be of order 1x10^12/cm2.

Created from the Publication Database of the Vienna University of Technology.